As an alternative to forcing shitdown, you may want to try laxatives.

There are a couple of things you can do. If it is frozen then try pressing ctrl+alt+1/2/3/4 to swith to a different terminal this will let you either restart your DE or reboot the system safely.

As far as debugging it I would typically start with looking at journal logs journalctl -b-1 should show you logs from the last boot.

There is https://en.wikipedia.org/wiki/Magic_SysRq_key but I’ve had some hit and miss success in actually getting it to work.

Normally I first try see if it is only the graphical interface that has crashed by pushing ctrl+alt+F1 or F2 or F3 to try and switch to another terminal. If I can switch, I log in and reboot or restart the window manager.

I also try SSH into the machine if I have another of around.

If I do reboot, then I use ‘journalctl -b-1 -e’ to see what happened at the time the system froze.

ctrl alt del used to do a graphics reset which often was all that was needed. ctrl alt f2 should put you in a terminal. If you had not done that I would give it a try and see if the whole system had crashed which would cause the terminal to not be responsive or if its just the grahics in which case you can login and reset the graphics.

You need to have a look at the logs using journalctl.

Type journalctl —help, have a look at the options (I think —since may be what you want) and post the logs if you want to.